second marriage secretly

My relative made second marriage secretly with a colleague in his Office. He had already a wife and a child from the first wife i.e. the marriage made by the family. Both my relative and his second wife made wrong statements on the Nikah Nama. They did not mention on the Nikah Nama that my relative was already married, though the second wife very well knew it as she was her old colleague. Somehow she managed to write too much HAQ MEHAR on the nikah nama. Now their second marriage has come to light and his family wants to get rid of second wife. But the problem is that Haq Mehar written on Nikah Name is too much beyond his capacity and he cannot pay it at any cost. Kindly help and advise how can he divorce his second wife. Thanks.